1. Technical Field
The embodiments herein generally relate to an index generation scheme for communication receivers, and, more particularly, to the generation of input/output indexes for prime factor Discrete Fourier Transform (DFT) without the need for additional memory for reordering blocks.
2. Description of the Related Art
The Discrete Fourier transform (DFT) is a powerful tool for many signal processing algorithms. In orthogonal frequency division multiplexing (OFDM) based modulation schemes for wireless data transmission, Inverse Discrete Fourier transform (IDFT)/Discrete Fourier transform (DFT) is used as a transformation tool. With advancement in OFDM modulation, different transmission standards use a different length of DFT to get an optimal performance in data transmission. For an example, the digital television standards use different sizes of DFT length for modulation (e.g., length of DFT for DVB-T standard is 2K/8K, length of DFT for ISDB-T standard is 2K/4K/8K, and length of DFT for DMB-T standard is 3780).
FIG. 1 illustrates a generic diagram of a Discrete Fourier transform (DFT) with Prime factor algorithm (PFA) 102 and non PFA 104. An N point DFT can be factorized into smaller size DFTs. Factors are grouped into one or more mutually prime factors 102 and zero or more non-prime factors 104. One of the efficient methods of implementing non prime factor DFTs 104 is using the Cooley-Tukey Fast Fourier transform (FFT). Prime factor DFTs 102 are implemented using a PFA. Even though the computation efficiency of PFA DFTs 102 is comparable to a Cooley-Tukey FFT, one important disadvantage of a PFA is that it requires a complicated data input/output indexing mechanism.
FIG. 2 is a table view illustrating digital transmission standards of DFT. The table view includes a DTV standard field 202, and a length of DFT field 204. The DTV standard field 202 includes one or more DTV standards (e.g., DVB-T, ISDB-T, DMB-T). The length of DFT field 204 includes one or more lengths (e.g., 2K/8K for DVB-T, 2K/4K/8K for ISDB-T, and 3780 for DMB-T). Digital Multimedia Broadcast-Terrestrial Digital television (DMB-T DTV) transmission uses a 3780-point DFT, which is not an integer power of 2 and is difficult to implement but provides more system performance compared to a 4096-point DFT. Current solution uses a lookup table to store required input/output indexes per stage. This scheme requires extra memory to store the index lookup tables. Accordingly there remains a need of developing an efficient, high performance parameterization method to perform DFTs which are non-integer powers of 2.